The present invention relates to couplers for joining the ends of successive lengths of pipe or conduit, and, in particular, to couplers for joining the ends of successive pipes in an exhaust system for vehicles.
It is well known that, in vehicle exhaust systems, particularly those for heavy duty vehicles, such as large trucks or earthmoving equipment, the internal combustion (i.c.) engines produce a significant amount of vibration in the exhaust pipes. Operation of the motors at continuous speeds for prolonged periods of time can, especially, produce what are known as harmonic vibrations which can cause significant deflections in extended lengths of exhaust pipe. Repeated deflections of the exhaust pipe will, in turn, cause the pipe to weaken with time and ultimately fail. Further, such harmonic vibrations will also be transmitted through the exhaust pipes to the mounting of the pipes, promoting the loosening of the mountings, which can result in the sudden displacement of one or more components of the exhaust system, with the potential for both personal injury and equipment damage.
In addition to the vibrations created by the motor of the vehicle, an exhaust system is also subjected to various tension, compression and bending forces which arise during the operation of the vehicle. While individual components might be made stronger and more massive to resist failure by fatigue, such construction would be undesirable due to weight considerations. Further, by making individual elements stiffer, the vibrations are merely transmitted to the exhaust system mountings or other components, not reduced or eliminated. Accordingly, it is desirable to isolate the exhaust system, or at least components of the system from such vibrations and forces.
It is known that if the pipes of an exhaust system are divided and separated by non-rigid connections, rather than as continuous extended lengths, the development of harmonic vibrations from the motor is precluded or reduced. Such non-rigid connections can be advantageously employed to absorb other tension, compression and bending forces, apart from and in addition to motor vibrations.
It is therefore desirable to provide a coupler for joining successive lengths of exhaust pipe, which coupler joins the pipes in a non-rigid fashion and is capable of absorbing tension, compression and bending forces, without transmitting them from one pipe to another.
An example of a prior art coupler is found in Usui, U.S. Pat. No. 4,792,161. In Usui, a pair of concentrically arranged spring coils are utilized to provide a mechanical connection between the pipes to be joined. One drawback of the coupler in Usui is that when the coils are in a stretched or bent configuration, gaps may form between individual bights of the coil, into which dirt, debris and moisture may invade, which may interfere with the operation of the coils, through abrasion, rusting and so forth. In addition, the coils (which are arranged one threaded within the other) are unprotected and exposed to the elements at all times, and are thus susceptible to damage from abrasion and other harmful physical contact. A further drawback of the coupler apparatus of Usui is that a sealing ring positioned between the overlapping pip ends, is relied upon to provide sealing means to prevent escape of the exhaust gases. The sealing ring is subjected to cyclical flexure, tension and compression forces which will ultimately compromise the seal and require replacement of the coupler.
Yet another prior art coupler apparatus is disclosed in Udell, U.S. Pat. No. 5,145,215. In Udell, an inner sleeve member is concentrically received by an outer sleeve member. A substantially porous, non-sealing, vibration absorbing spacer member is arranged between the sleeve members where they overlap, to preclude direct contact between the sleeve members. The spacer member is non-sealing to preclude deterioration while minimizing interference with the reciprocation and articulation of the sleeve members. A flexible, extensible bellows member mechanically connects the sleeve members at their distant non-overlapped ends. A closure member, typically of braided metal wire, surrounds the bellows member for protecting the extensible bellows member from damage from external elements and forces.
While the apparatus of the Udell patent is capable of accommodating extension, compression and relative pivoting of the pipe ends which are connected, the Udell apparatus has but a single "pivot point" and accordingly, does have a limit as to the amount of relative pivoting which can be accommodated. Further, within the limits of compressibility of the spacer member, the axes of the two pipes which are connected, cannot move to a non-intersecting (i.e., skewed) relationship. Still further, the apparatus of Udell is better adapted for the accommodation of extension, than it is to the accommodation of compression. In the possible, though typically uncommon, event of overcompression of the coupler, there is a possibility of jamming or distortion of components, which may adversely affect the subsequent performance of the coupler, and may even lead to premature degradation and failure of the coupler. There is no positive "stop" structure provided, to prevent such jamming.
It would be desirable to provide a flexible coupler apparatus which has an enhanced, more robust configuration, in order to provide for the decoupling of an exhaust system from a source of vibration, such as an i.c. engine.
It would also be desirable to provide a flexible coupler apparatus for exhaust systems which accommodates the orientation of the ends of the pipes to be connected into a non-intersecting (skewed) relationship.
It would still further desirable to provide a flexible coupler apparatus which is provided with structure which will provide an affirmatively acting stop against overcompression of the coupler apparatus.
These and other objects of the invention will become apparent in view of the present specification, claims and drawings.